Cigarette filter plug and process and
apparatus for making same



June 10, 1969 D DUNLAP Re. 26,604

CIGARETTE FILTER PLUG AND PROCESS AND APPARATUS FOR MAKING SAME OriginalFiled Sept. 30, 1958 x 1.11 IJIIfI United States Patent 26,604 CIGARETTEFILTER PLUG AND PROCESS AND APPARATUS FOR MAKING SAME Donald T. Dunlap,Charlotte, N.C., assignor to Celanese Corporation, a corporation ofDelaware Original No. 3,190,294, dated June 22, 1965, Ser. No. 764,338,Sept. 30, 1958. Application for reissue June 20, 1967, Ser. No. 653,588

Int. Cl. A27f 7/04, 13/06; Btlld 27/00 US. Cl. 131-267 1 Matter enclosedin heavy brackets appears in the original patent but forms no part ofthis reissue specification; matter printed in italics indicates theadditions made by reissue.

The present invention relates to a novel, shape-retaining fiibrousmaterial and to a process and apparatus whereby it can be formed. Moreparticularly, it relates to the formation of a shape-retaining structureof thermoplastic filimentary material suitable for use as a cigarettefilter plug.

Cellulose acetate has gained wide acceptance as a filter for tobaccosmoke, being incorporated as a mouthpiece on cigarettes. In oneprocedure for manufacturing such cigarettes, a tow or bundle of severalthousand continuous cellulose acetate filaments is spread flat, sprayedwith a plasticizer, brought into a predetermined shape by passagethrough a corresponding shaped aperture in a device referred to as acondenser, and fed into a conventional cigarette wrapping machinetogether with cigarette paper. The paper wraps the tow into a continuousrod and is then secured to maintain the shape in the same manner thattobacco is held in paper to form cigarettes. After the paper-wrappedfilter rod is cut into plugs of the desired length, the plugs are curedto effect stiffening of the filter through bonding of the filaments attheir points of contact and the plugs are incorporated into cigarettesin well-known manner by being wrapped in cigarette paper with tobacco.

By proceeding as outlined, time is consumed in the initial wrapping ofthe tow in paper, and where the paper is secured by glueing, in theapplication of glue to seal the paper and in the drying of the glue. Inaddition, paper and glue are required which, though not contributing tofiltration, add to the cost of the filter.

In another procedure, a bundle of filaments is heated while being passedthrough a stationary shaping member. The heat is applied in such amountthat the surface filaments are fused to form an impervious sheath. Whilethe sheath serves to retain the shape without a paper wrapping, thefilaments employed in forming the sheath lose their filamentarycharacter and will not contribute to filtration of smoke. The resultingoverall filtration efficiency will thus be lower than for paper wrappedfilters wherein all filaments are effective during filtration.

Accordingly, the primary object of the present invention is theprovision of a novel process and apparatus for the rapid production ofpaperless shape-retaining cigarette filter rods and plugs without lossof the filamentary character of the component filaments.

Other and further object of the invention will be apparent from thedescription which follows.

In accordance with the present invention, a continuous tow of limpthermoplastic filaments is spread flat and sprayed with a plasticizer,i.e. partial solvent or swelling agent which is preferably non-volatileor an active solvent which is preferably volatile. The plasticized towis then passed through heated grooved movable members such as rollers orwheels which condense the tow into a predetermined transverse shape suchas a circle, ellipse, etc., and heat the surface of the tow sufficientlyto cohere the outermost filaments to each other at their points of con-0 Claims Re. 26,604 Reissued June 10, 1969 "ice tact without destroyingtheir filamentary character. The heat may be supplied by a quartztubular heating element or by equivalent heating means.

Although there is movement of the heated grooved rollers or wheels, thesurface of the tow is stationary with respect to those portions of theheated surfaces which shape the same and cohere the surface filamentsthereof. Non-circular clamping members movable with the tow uponclamping engagement therewith, such as links on an endless chain orbelt, may also be used to serve the same purpose through circularelements are preferred since these lead to continuity of operation andmore rapid production rates. As will now be evident, there is no wipingaction of the shaping member relative to the filaments and filterelements of high overall filtration efficiency are rapidly and simplyobtained.

Upon cooling the cohered filaments cause the structure to retain theshape it had during heating. The filter rod is then cut into plugs forincorporation into cigarettes.

It is essential in accordance with the invention that the filamentarytow be treated with plasticizer to permit bonding of the superficialfilaments initially under such mild conditions that they will not losetheir filamentary character as in formation of a skin. The plasticizeralso permits curing to be effected without heating so intensely asdisadvantageously to alter the physical character of either the inner orouter filaments.

The invention will now be described more fully with reference to theaccompanying drawing wherein:

FIG. 1 is a schematic elevation of an apparatus for making cigaretteplugs and illustrating the procedure of the present invention;

FIG. 2 is a section taken through the forming and heating rolls alongthe line 2-2 in FIG. 1;

FIG. 3 is a perspective view of a plug produced by the apparatus of FIG.1; and

FIG. 4 is a transverse section on a greatly enlarged scale through aportion of the plug shown in FIG. 3.

Referring now more particularly to the drawing, in FIG. 1 there is showna crimped cellulose acetate tow 10 composed, for example, of 9000continuous filaments of 8 denier. The tow 10 is removed from itsshipping container 11 and is opened or spread fiat by opener 12 ofconventional construction. The tow 10 then passes continuously throughbox 13 into which plasticizer is sprayed as a mist, the opened towpicking up the plasticizer. The plasticized tow next advances through acircular guide or condenser 14 toward the heated elements. 15.

As can be seen the heating elements 15 are constituted, in the preferredform of the invention which is illustrated, by numerous pairs of smallgrooved rollers or wheels 16, the groove being a peripheral groove 17.In the drawing, two pairs of wheels are placed so that their rotationalplanes are offset at an angle, one in horizontal and the other invertical position. As will be evident, these angles may be varied andmore than two pairs of rollers or wheels may be employed for the purposeof ironing out or eliminating any markings or distortions caused by theforming wheels or rolls. The pairs of rollers or wheels 16 arepreferably closely spaced with respect to one another so that the tow isstill warm on reaching the second pair of rollers and so that formationof a coherent mass can be effected rapidly without repeated heatingwhich would form an unduly thick skin on the surface and would unite theinner filaments at so many points as to reduce the surface area forfiltration and as to form a stiff rigid rod. As will be evident, therollers or wheels in each of the pairs 16 are opposed to one another sothat the filamentary tow is shaped therebetween.

The rollers or wheels 16 may be driven at machine speed, e.g. at a ratesuch that the peripheral velocity of the wheels, particularly at thebottom of the grooves 17 formed therein, coincides with the linearvelocity of the tow. On the other hand, the rollers or wheels 16 may befree rolling in which event the rate of rotation thereof is controlledby the passage of the tow between the pairs of rollers and other meanssuch as a conventional cigarette making machine, which is normallydirectly in back of the filter forming unit to take the rod and cut itinto plugs in the manner that wrapped tobacco is cut into short lengths,or driven unheated feed rollers may be employed to pull the filamentarytow through the heated forming rollers. The grooves in the various pairsof rollers may all be shaped to define a substantially circular openingof somewhat larger diameter with the trailing pairs of rollers beinggrooved to define a substantially circular opening of somewhat smallerdiameter.

In the form of the invention which is illustrated, the forming rollersor wheels 16 include electric heating elements 18 imbedded therein, anelectrical circuit 19 being employed whereby the forming rollers 16 areheated to filament cohering temperature.

Instead of or in addition to electrical heating, the various pairs ofrollers 16 may be confined within an oven, preferably a radiant heatedover, and the rollers heated by the heat of the oven. If desired,additional pairs of rollers may be employed to facilitate cooling of therod, these additional rollers or wheels having refrigerant passingtherethrough to assist in the cooling operation. However, and as isillustrated in the drawing, air cooling of the shape-retaining rod ispermissible.

The surfaces of the grooves on all of the rollers or wheels aredesirably coated with a release agent, such as a silicone release agentor these surfaces may be plated or sand blasted to reduce thepossibility that the filamentary tow will stick to the rollers orwheels.

The tow is now in the form of a paperless shape-retaining cigarettefilter rod 20 which passes to the cutter 21 of a conventional cigarettemaking machine where it is severed into filter plugs 22. These plugs 22can be incorporated into cigarettes in the same manner heretoforeemployed with paper-wrapped plugs, after a cure to stiffen the innerfilaments by bonding them to each other.

As shown on an enlarged scale in FIG. 3, the plugs 22 is composed of aplurality of crimped Wavy filaments 23 extending longitudinally. Becauseof the crimps the filaments contact wtih each other at a plurality oflocations such as at 24 and they are cohered without loss of theirfilamentary character so that all filaments contribute to the filteringaction. As can be seen in FIG. 4, the outer surface portions of theoutermost filaments are seen to i be slightly filattened so as to besubstantially coincident with the continuous closed curve defining theperiphery of the filter, i.e., curve 25 shown in broken lines andslightly offset for ease of illustration.

The tow can be formed of any thermoplastic filamentary material such asnylon, linear polyesters such as polyethylene terephalate, and the like,but the preferred materials are cellulose esters of organic acids andparticularly cellulose acetate, the acetyl value of which can range fromabout 50 to about 62.5% by weight calculated as acetic acid.

The sprayed plasticizer softens the surfaces of the filaments andpermits cohesive joinder of the outermost filaments under thermalconditions which will not destroy the filamentary character of thefilaments. The composition of the plasticizer will depend up thecomposition of the tow. With cellulose acetate the preferredplasticizers include swelling agents such as glycreol triacetate,triethyl citrate, dimethoxy-ethyl phthalate, methyl phthalyl ethylglycolate, and the like, and active solvents such as acetone, methylenechloride, dioxane, dimethyl formamide, and the like. The plasticizer canbe applied in an amount ranging from about 3 to by weight of the tow.When the plasticizer comprises a low boiling solvent preferably onlymoderate temperatures are utilized to effect bonding, thereby preventingcondensation pickup due to rapid cooling caused by rapid evaporation ofsolvent at high temperatures. Where the plasticizer comprises a swellingagent the temperature of heating can range from about 350 to 600 F. andpreferably 400 to 500 F. and the duration of heating totals from aboutone to about ten seconds. As will be evident, the duration of heatingsupplied to the tow by any given pair of rollers 16 is only a fractionof a second but the tow remains within the desired temperature range forthe indicated time interval because of the close positioning of thesuccessive rollers.

In making a filter for a cigarette of conventional size, the tow canrange in denier from about 60,000 to 120,000 and the individualfilaments thereof can range from about 3 to 16 denier. The tow employedis preferably a crimped tow having from about 6 to 12 crimps per inch oftow, the length being determined by placing a specimen of the tow undersufficient tension to remove the crimps therefrom.

The following example is given by way of illustrating the practice ofthe present invention.

EXAMPLE A tow of 10,000 continuous filaments, 80,000 total denier, ofcellulose acetate of an acetyl value of 54-56%, having 8-l0 crimps perinch based on the tensioned length of the tow, is opened and spread outto a width of 12 to 14 inches and glycerol triacetate is applied theretoby spraying to the extent of 10% by weight of the tow. The plasticizedtow is then passed through the heated rollers 15 as shown in FIG. I. Thesurface of the heated rollers which contacts the tow is maintained at atemperature of about 450 F. by means of a tubular quartz infrared lampand the plasticized tow is advanced at the rate of about 1 feet persecond through 4 pairs of freely rotatable rollers successively offsetat angles. Each roller is 2% inches in diameter. After leaving the lastpair of rollers, the tow, which is now a shape-retaining rod about 25mm. in circumference is cut into plugs 90 mm. long which plugs are curedat room temperature in 2 hours.

Using another swelling agent such as the citrate, phthalate or glycolatenamed hereinabove gives substantially the same results after curing for1 hour at F.

The product is characterized by a smooth surface free of belt imprint.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein Without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patentis:

1. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments [of total denier ranging from about60,000 to 120,000 and of individual denier ranging from about 3 to 16,]all of said filaments because of their crimp contacting other filamentsat a plurality of spaced locations, the outermost filaments beingplasticized and cohered into a shape-retaining surface without loss oftheir filamentary charac ter, said plug having a smooth surface.

2. A plug according to claim 1 in which said filaments comprisecellulose acetate.

3. The process of forming shape-retaining paperless cellulose acetatecigarette filter plugs which comprises opening a limp tow of continuous,crimped cellulose acetate filaments, spraying a plasticizer forcellulose acetate onto said opened tow, conveying said plasticized towbetween a plurality of pairs of rotatable heated opposed peripherallygrooved rollers which cooperate to shape sai-d tow into predeterminedconfiguration and to cohere the outermost filaments of said tow to eachother at their points of contact without destroying their filamentarycharacter, said rollers being rotated at a peripheral speed equal to thelinear speed of said tow in passing therebetween, the plane in whicheach pair of rollers rotates being olfset relative to the rotationalplanes of adjacent pairs of rollers, and cooling and severing saidcooled tow into plugs of predetermined length to produce a cigarettefilter plug of high overall filtration efficiency.

4. The process recited in claim 3 in which about 3 to 30% by weight ofsaid plasticizer is applied to said tow.

5. Apparatus for forming shape-retaining paperless cigarette filterplugs from a continuous tow of limp thermoplastic filaments, comprisingmeans for opening said tow, means for applying plasticizer to saidopened tow. a plurality of pairs of heated opposed peripherally groovedrollers for shaping said tow into predetermined configuration wherebythe outermost filaments of said tow are caused to cohere to each otherat their points of contact Without destroying their filamentarycharacter, the plane in which each pair of rollers rotates being oflsetrelative to the rotational plane of adjacent pairs of rollers, means foradvancing said tow between said pairs of rollers at a linear speed equalto the peripheral speed of said rollers, and means for severing said towinto plugs of predetermined length to produce a cigarette filter plug ofhigh overall filtration efiiciency.

6. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments of total denier ranging from about60,000 to 120,000, all of said filaments because of their crimpcontacting other filaments at a plurality of spaced locations, theoutermost filaments being plasticized and cohered into a shape-retainingsurface without loss of their filamentary character, said plug having asmooth surface.

7. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments of individual denier ranging from about3 to 16, all of said filaments because of their crimp contacting otherfilaments at a plurality of spaced locations, the outermost filamentsbeing plasticized and cohered into a shape-retaining surface withoutloss of their filamentary character, said plug having a smooth surface.

8. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments of total denier ranging up to about120,000 and of individual denier ranging from about 3 to 16, all of saidfilaments because of their crimp contacting other filaments at aplurality of spaced locations, the outermost filaments being plasticizedand cohered into a shape-retaining surface without loss of theirfilamentary character, said plug having a smooth surface.

9. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments of total denier ranging from about60,000 to 120.000 and of individual denier ranging up to about 16, allof said filaments because of their crimp contacting other filaments at aplurality of spaced locations, the outermost filaments being plasticizedand cohered into a shape-retaining surface without loss of theirfilamentary character, said plug having a smooth surface.

10. A shape-retaining cigarette filter plug comprising a plurality ofcrimped thermoplastic filaments of total denier ranging from about60,000 to 120,000 and of individual denier ranging from about 3 to 16,all of said filaments because of their crimp contacting other filamentsat a plurality of spaced locations, the outermost filaments beingplasticized and cohered into a shape-re taining surface without loss oftheir filamentary character, said plug having a smooth surface.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

MELVIN D. REIN, Primary Examiner.

US. Cl. X.R.

